There are many situations in which it is desirable to remove unwanted tissue from a patient. Uterine fibroids and uterine polyps represent two such types of unwanted tissue. Uterine fibroids are well-defined, non-cancerous tumors that are commonly found in the smooth muscle layer of the uterus. Uterine polyps are wispy masses that are commonly found extending from the inner lining of the uterus. In many instances, uterine fibroids and uterine polyps can grow to be several centimeters in diameter and may cause symptoms like menorrhagia (prolonged or heavy menstrual bleeding), pelvic pressure or pain, and reproductive dysfunction. It is believed that uterine fibroids occur in a substantial percentage of the female population, perhaps in at least 20 to 40 percent of all women, and that uterine polyps occur in up to 10 percent of all women.
One type of treatment for uterine fibroids and uterine polyps is hysteroscopic resection. Hysteroscopic resection typically involves inserting a hysteroscope (i.e., an imaging scope) into the uterus through the vagina, i.e., transcervically, and then cutting away the unwanted tissue from the uterus using a device delivered to the unwanted tissue by the hysteroscope. Hysteroscopic resections typically fall into one of two varieties. In one variety, an electrocautery device in the form of a loop-shaped cutting wire is fixedly mounted on the distal end of the hysteroscope. The combination of the hysteroscope and the electrocautery device is typically referred to as a resectoscope. The transmission of electrical current to the uterus with a resectoscope is typically monopolar, and the circuit is completed by a conductive path to the power unit for the device through a conductive pad applied to the patient's skin. In this manner, tissue is removed by contacting the loop with the part of the uterus wall of interest. Examples of such devices are disclosed, for example, in U.S. Pat. No. 5,906,615, inventor Thompson, issued May 25, 1999.
In the other variety of hysteroscopic resection, an electromechanical cutter is inserted through a working channel in the hysteroscope. The electromechanical cutter typically includes (i) a tubular member having a window through which tissue may enter and (ii) a cutting instrument positioned within the tubular member for cutting the tissue that has entered the tubular member through the window. In use, the cutter is positioned near the part of the uterus wall of interest. Tissue is then drawn, typically by suction, into the window, and then the tissue drawn into the window is cut with the cutting instrument. Examples of the electromechanical cutter variety of hysteroscopic resection are disclosed in, for example, U.S. Pat. No. 7,226,459, inventors Cesarini et al., issued Jun. 5, 2007; U.S. Pat. No. 6,032,673, inventors Savage et al., issued Mar. 7, 2000; U.S. Pat. No. 5,730,752, inventors Alden et al., issued Mar. 24, 1998; U.S. Patent Application Publication No. US 2009/0270898 A1, inventors Chin et al., published Oct. 29, 2009; U.S. Patent Application Publication No. US 2009/0270812 A1, inventors Litscher et al., published Oct. 29, 2009; U.S. Patent Application Publication No. US 2006/0047185 A1, inventors Shener et al., published Mar. 2, 2006; and PCT International Publication No. WO 99/11184, published Mar. 11, 1999, all of which are incorporated herein by reference.
In both of the above-described varieties of hysteroscopic resection, prior to tissue removal, the uterus is typically distended to create a working space within the uterus. Such a working space typically does not exist naturally in the uterus because the uterus is a flaccid organ. As such, the walls of the uterus are typically in contact with one another when in a relaxed state. The conventional technique for creating such a working space within the uterus is to administer a fluid to the uterus through the hysteroscope under sufficient pressure to cause the uterus to become distended. Examples of the fluid used conventionally to distend the uterus include gases like carbon dioxide or, more commonly, liquids like water or certain aqueous solutions (e.g., a saline or other physiologic solution or a sugar-based or other non-physiologic solution).
One of the benefits of fluid distension is the tamponade effect that the distension fluid provides on resected vascular tissue. Since the distension fluid is typically maintained at a pressure that exceeds the patient's mean arterial pressure (MAP), the fluid pressure provided by the distension fluid prevents the leakage of arterial blood from the resected tissue from flowing or oozing into the uterine cavity. When arterial blood flows or oozes into the cavity, it mixes with the distension fluid and renders visualization more difficult and, if not constrained, the flowing or oozing blood will force the suspension of the procedure. Thus, maintenance of fluid pressure above the intracavity arterial pressure is critical for the maintenance of a clear visual field.
Nevertheless, one shortcoming with existing hysteroscopic tissue removal systems, particularly of the electromechanical cutter variety, is that it is often difficult to maintain fluid distension of the uterus during the resection procedure. This is because such systems typically employ a vacuum source that continuously subjects the electromechanical cutter to suction, even when the cutting mechanism of the electromechanical cutter is not switched on. The purpose of such suction is to draw tissue into the cutter, typically through the window, and to facilitate the removal of resected tissue from the uterus. However, such suction also typically has the unwanted effect of removing some of the distending fluid from the uterus along with the resected tissue. Moreover, because suction is continuously applied to the cutter, even when the cutting mechanism is not being operated, fluid tends to be continuously removed from the uterus whenever the cutter is inserted into the patient. If such fluid cannot be replenished quickly enough, the fluid pressure within the uterus may drop to an undesired level. In particular, a steep drop in uterine fluid pressure will result in the leakage of blood into the uterine cavity, causing a loss of visualization and ultimately stoppage of the procedure if the surgeon can no longer properly visualize the treatment site. Moreover, depending on the extent and speed of the drop in uterine fluid pressure, there may be a significant lapse of time before the uterine fluid pressure can be restored to a desired level such that adequate visualization is possible. Such lapses in time are clearly undesirable as they interrupt the resection procedure, as well as lengthen the overall time for the procedure and increase the risk that distending fluid may be taken up by a blood vessel in the uterus, i.e., intravasation, which uptake may be quite harmful to the patient.
One approach to the above problem has been to provide the electromechanical cutter with a mechanism actuated by an electrical switch that causes the window in the cutter to be closed off when the cutting mechanism is turned off. In this manner, when the cutting mechanism is switched off, distension fluid from the uterus cannot escape from the uterus through the resection window of the cutter, and adequate uterine fluid pressure may be maintained. Unfortunately, however, the cost of the aforementioned electrical switch, as well as the cost of several other components of the cutter, may make the cost of the above-described electromechanical cutter prohibitive for certain procedures, such as polypectomies, for which the costs covered by most insurers are typically relatively low.